In recent years, a spout-attached pouch, which is referred to as a spout pouch, has been in widespread use. In the spout-attached pouch, a spout made of resin is integrally attached to an upper portion of a pouch composed of a resin film which is referred to as a soft packaging and a barrier material such as aluminum, and after the pouch is filled with the contents, a resin cap for sealing is attached to an end portion of the spout.
The feature of the spout-attached pouch is that it is lightweight and that it can be made into a flat shape in the states before use and after use, and thus it does not take up space. Therefore, a reduction in transportation charges or a reduction in waste is possible. Further, in the spout-attached pouch, since the pouch itself is soft, the extrudability (squeezability) of the contents is excellent, and for example, in a case of goods such as mayonnaise or ketchup, it is possible to reduce the amount of air in a container, compared to that in a glass bottle or a hard container. Therefore, the spout-attached pouch is suitable as a container for like of mayonnaise or ketchup, which are easily oxidized, cooking oil, alcoholic liquors, seasonings, or dairy products such as condensed milk.
Although, in the spout-attached pouch, in a pouch part, it is possible to provide sufficient gas barrier properties by selecting and laminating a film having gas barrier properties, on the other hand, in a spout part, if it is configured of a single-substance resin such as polyethylene or polypropylene, in terms of gas barrier properties, this cannot be considered to be sufficient.
Further, in a case where the contents are fruit juice or the like having a low viscosity, since the contents in the spout-attached pouch will circulate due to vibration during distribution, changes in temperature at the time of being stocked, or the like, it is difficult for the deterioration of the contents due to oxidation to be manifested. However, in a case where the contents are the above-mentioned mayonnaise, ketchup, or the like, the viscosity thereof is high, and therefore, the contents are prone to stay in the vicinity of the spout for a long period of time and there is a possibility that the contents may deteriorate due to oxidation.
As a spout for a pouch for coping with these problems, a spout in which a metal pipe having gas barrier properties is embedded in a peripheral wall surrounding a pouring hole of the spout has been devised (refer to Patent Document 1, for example).
In this spout for a pouch, although the ingress of oxygen from the outside can be blocked by the embedded metal pipe, the manufacturing costs are liable to be higher due to the use of the metal pipe.
For this reason, as an alternative spout for a pouch to this, a spout in which a blocking tube made of a resin material which has excellent gas barrier properties is embedded in a peripheral wall surrounding a pouring hole of the spout has been devised (refer to Patent Documents 2 and 3, for example).
In the spouts for a pouch disclosed in Patent Documents 2 and 3, the blocking tube which is embedded in a base resin of the peripheral wall has a tubular blocking layer made of a material having barrier properties, such as ethylene-vinyl alcohol copolymer resin (EVOH), and a tubular covering layer which is disposed in contact with at least the inner peripheral surface of the blocking layer, and the covering layer is formed of a resin material of the same quality as the base resin, which is easily joined to the base resin.
In a case of manufacturing this spout for a pouch, the blocking tube is disposed in a mold in a state of being externally fitted to a shaft part of the mold for molding the pouring hole, and in this state, a melted base resin is injected and filled into a cavity of the mold. In this way, the melted base resin goes around the end face in an axial direction and the outer periphery side of the blocking tube in the mold, and when the base resin is solidified in the mold, the base resin is joined to the covering layer of the blocking tube.